The work is related to our long term interest in carrying out metabolic and biochemical studies in hematologic diseases and neoplasia in conjuction with chemotherapy. We follow the relationship of biochemical changes (particularly alterations of tryptophane metabolites) in urine, blood, and tumor to the clinical changes occurring in patients with malignant carcinoid syndrome and the effects on these of various established and new chemotherapeutic agents. We plan to continue similar studies in the P815 mast cell tumor. We hope to clarify the problem presented by conflicting reports concerning abnormalities of tryptophane metabolism in patients with aplastic and refractory anemias. We also carry out studies aimed at elucidating the fundamental defect in the red cells of patients with paroxysmal nocturnal hemoglobinuria.